Gas sensors specific to carbon dioxide (CO2) gas are operated, according to the prior art, mainly in accordance with the following principles:
Infrared absorption: the sensor is specific, highly sensitive and long-term stable, but expensive (>60 USD).
Electrochemical sensors: the sensor is specific and has medium sensitivity, but exhibits low long-term stability, and the cost is somewhat lower than that of IR sensors.
Thermal conductivity: the sensors are not very specific and are insensitive, but are long-term stable and relatively low in cost.
Therefore, in general, what is needed is a sensor which meets all of the criteria of specificity, sensitivity, long-term stability, and low cost. Such a CO2 sensor at a price of less than 10 USD would open up new market segments, e.g. control of air conditioning systems in buildings and automobiles.